1. Field of the Invention
The invention relates to a fan construction, more particularly to a fan which is capable of directing air flow in the axial and radial directions and which generates little noise and vibrations when rotated at high speeds.
2. Description of the Related Art
Referring to FIG. 1, a conventional motor 1 is shown to be provided with a fan 12 and includes a motor housing 10, a driving spindle 11, an upstream cover 13, and a downstream cover 14. The fan 12 is mounted securely on the driving spindle 11. The upstream cover 13 is attached to the upstream end 101 of the motor housing 10, while the downstream cover 14 is attached to the downstream end 102 of the motor housing 10. When the motor 1 is activated, the driving spindle 11 rotates the fan 12, thereby causing air to be drawn into the motor housing 10 via the downstream cover 14 in order to cool the motor 1. Hot air flows out of the motor housing 10 via the upstream cover 13.
The fan 12 determines the direction of air flow through the motor housing 10. Presently, there are two different kinds of fan constructions. The first kind directs air to flow in an axial direction, while the second kind directs air to flow in a radial direction.
FIG. 2 is a sectional view which illustrates a conventional motor 2 that employs an axial flow-type fan 21. When the motor 2 is activated, the fan 21 draws air into the motor housing 20 via an air inlet portion 22 at the downstream end of the latter. The fan 21 directs air to flow out of the motor housing 20 via an air outlet portion 23 at the upstream end of the latter.
Aside from the difference in the constructions of the axial flow-type fan and the radial flow-type fan, the construction of the motor housing for the radial flow-type fan is slightly different from that for the axial flow-type fan. When air that is drawn by the radial flow-type fan strikes the fan blades of the latter, the air is dispersed in the radial direction. Air then flows out of the motor housing via air outlet holes that are located around the fan.
Since conventional fans are incapable of directing air flow in both axial and radial directions, the stability of the conventional fans in the axial and radial directions cannot be ensured, thereby resulting in strong vibrations and in the generation of relatively loud noise when the conventional fans are in use.